The Official ChromaPure thread - Page 130

Originally Posted by TomHuffman 

Small windows are fine. What is not fine is full fields.

Originally Posted by TomHuffman 

I just listened to Scott Wilkinson response to manufacturer's boast about their displays having a much wider gamut. Scott correctly points out that content (broadcast and Blu-ray) are mastered to a narrower gamut than what wide gamut displays are capable of, so he aks, what good is a wide gamut display? The manufacturer's response is that the content was originally filmed using a much wider gamut, which was shrunk only when transferred to Blu-ray or mastered for broadcast. The wide gamut display, the argument goes, merely restores these missing colors.

Let me explain why this is nonsense. In the first place this is nothing new. Manufacturers have been offering wide gamut displays for a long time. The original JVC LCoS projector, the RS1, had an extremely wide gamut. This is an old argument, but manufacturers keep recycling it as a way of convincing gullible consumers to purchase their products.

Second, while it is true that content is originally filmed using a wider gamut, most of the colors we see don't take advantage of the extra colors. Skin tones, trees, grass, sky are all composed of colors that fall well within the Rec. 709 HD standard. Only a relatively small percentage of the colors are lost when the gamut is shrunk to fit the HD standard.

Third, and most importantly, when remapping colors from a wide gamut source to a narrower gamut medium, the ONLY colors that are affected are those small number that are outside the HD gamut. The rest of the colors--the vast majority--stay the same. Think for a moment why this is true. If a skin tone naturally falls well within the HD gamut, you wouldn't want to change that color when remapping wide gamut source material to HD. That would visibly distort the skin tone. Only the relatively few very saturated colors will be remapped to fall within the HD boundary.

This explains why attempting to restore the original gamut by playing HD content on a wide gamut display is a bad idea. What the wide gamut display does is oversaturate ALL colors--including the skin tones I mentioned in the previous example. The display has no way of distinguishing between those colors that were compressed during the mastering process and those that weren't, so it indiscriminately increases the saturation of all of the colors.

BTW, there is one practical advantage to a wide gamut display for some users. If you have a good color management system, then it is useful to have as a starting point oversaturated colors that can then be desaturated to the correct HD standards. Other than this manufacturer claims about wide gamut displays are unhelpful marketing hype that should be ignored.

Originally Posted by TomHuffman 

I just listened to Scott Wilkinson response to manufacturer's boast about their displays having a much wider gamut. Scott correctly points out that content (broadcast and Blu-ray) are mastered to a narrower gamut than what wide gamut displays are capable of, so he aks, what good is a wide gamut display? The manufacturer's response is that the content was originally filmed using a much wider gamut, which was shrunk only when transferred to Blu-ray or mastered for broadcast. The wide gamut display, the argument goes, merely restores these missing colors.

Let me explain why this is nonsense. In the first place this is nothing new. Manufacturers have been offering wide gamut displays for a long time. The original JVC LCoS projector, the RS1, had an extremely wide gamut. This is an old argument, but manufacturers keep recycling it as a way of convincing gullible consumers to purchase their products.

Second, while it is true that content is originally filmed using a wider gamut, most of the colors we see don't take advantage of the extra colors. Skin tones, trees, grass, sky are all composed of colors that fall well within the Rec. 709 HD standard. Only a relatively small percentage of the colors are lost when the gamut is shrunk to fit the HD standard.

Third, and most importantly, when remapping colors from a wide gamut source to a narrower gamut medium, the ONLY colors that are affected are those small number that are outside the HD gamut. The rest of the colors--the vast majority--stay the same. Think for a moment why this is true. If a skin tone naturally falls well within the HD gamut, you wouldn't want to change that color when remapping wide gamut source material to HD. That would visibly distort the skin tone. Only the relatively few very saturated colors will be remapped to fall within the HD boundary.

This explains why attempting to restore the original gamut by playing HD content on a wide gamut display is a bad idea. What the wide gamut display does is oversaturate ALL colors--including the skin tones I mentioned in the previous example. The display has no way of distinguishing between those colors that were compressed during the mastering process and those that weren't, so it indiscriminately increases the saturation of all of the colors.

BTW, there is one practical advantage to a wide gamut display for some users. If you have a good color management system, then it is useful to have as a starting point oversaturated colors that can then be desaturated to the correct HD standards. Other than this manufacturer claims about wide gamut displays are unhelpful marketing hype that should be ignored.

Originally Posted by mlg33 

Thank you.
What is the latest version of Chromapure ?
I'm using the 2.3.2.4xxx version.

And as far as your post just above is concerned, are you talking about the 4:4:4 option in some BRD players ?
Do you recommend staying at 4:2:2 instead ?

Remi.

If there is no obvious difference between YCbCr modes and RGB modes, YCbCr 4:2:2 is the best mode to use... period. It delivers 12-bit video while the other options are all limited to 8 bits (discussed in other forum threads and is NOT what most people THINK happens -- most people think all format options are 8-bits unless you enable a higher-bit mode in the player... but that's not true). Even Lumagen, makers of the best video processors available in the consumer market, recommend 4:2:2 unless there is a compelling reason to use some other mode (like RGB looks better with some specific video displays).

In my experience, about 60% of the time, every mode looks identical. Somewhere around 5%-10% of the time, RGB looks better (video display determines this) and the remainder of the time YCbCr looks better. So you have a 90-95% chance of YCbCr 4:2:2 being the best option.

Originally Posted by TomHuffman 

I just listened to Scott Wilkinson response to manufacturer's boast about their displays having a much wider gamut. Scott correctly points out that content (broadcast and Blu-ray) are mastered to a narrower gamut than what wide gamut displays are capable of, so he aks, what good is a wide gamut display? The manufacturer's response is that the content was originally filmed using a much wider gamut, which was shrunk only when transferred to Blu-ray or mastered for broadcast. The wide gamut display, the argument goes, merely restores these missing colors.

Let me explain why this is nonsense. In the first place this is nothing new. Manufacturers have been offering wide gamut displays for a long time. The original JVC LCoS projector, the RS1, had an extremely wide gamut. This is an old argument, but manufacturers keep recycling it as a way of convincing gullible consumers to purchase their products.

Second, while it is true that content is originally filmed using a wider gamut, most of the colors we see don't take advantage of the extra colors. Skin tones, trees, grass, sky are all composed of colors that fall well within the Rec. 709 HD standard. Only a relatively small percentage of the colors are lost when the gamut is shrunk to fit the HD standard.

Third, and most importantly, when remapping colors from a wide gamut source to a narrower gamut medium, the ONLY colors that are affected are those small number that are outside the HD gamut. The rest of the colors--the vast majority--stay the same. Think for a moment why this is true. If a skin tone naturally falls well within the HD gamut, you wouldn't want to change that color when remapping wide gamut source material to HD. That would visibly distort the skin tone. Only the relatively few very saturated colors will be remapped to fall within the HD boundary.

This explains why attempting to restore the original gamut by playing HD content on a wide gamut display is a bad idea. What the wide gamut display does is oversaturate ALL colors--including the skin tones I mentioned in the previous example. The display has no way of distinguishing between those colors that were compressed during the mastering process and those that weren't, so it indiscriminately increases the saturation of all of the colors.

BTW, there is one practical advantage to a wide gamut display for some users. If you have a good color management system, then it is useful to have as a starting point oversaturated colors that can then be desaturated to the correct HD standards. Other than this manufacturer claims about wide gamut displays are unhelpful marketing hype that should be ignored.

Originally Posted by realzven 

It depends on the Bluray players, some have good color space conversions, other have bad conversions...

it's better to test and choose the color space that not have chromatic errors...

see doug post : http://www.avsforum.com/t/1454748/blurry-player-settings-for-calibration#post_22891380

Originally Posted by mlg33 

Thank you.
What is the latest version of Chromapure ?
I'm using the 2.3.2.4xxx version.

And as far as your post just above is concerned, are you talking about the 4:4:4 option in some BRD players ?
Do you recommend staying at 4:2:2 instead ?

Remi.

Originally Posted by JimP 

Nice rightup Tom.

What colors would benefit from a Wide colorspace system?

On my 2012 Panasonic 65VT50, there is a menu setting to change the color space to "Wide". The description is to increase greens and blues. Sounds like an artificial way to pump up football games and nature content.

Originally Posted by Geof 

Yes Tom, once that color info is discarded/remapped to fit in a REC709 colorspace it can never be recreated properly. Hopefully if 4K comes along it will have a wider colorspace with more bit depth (personally I'd rather see 10-12 bit color before a wider CS tho).

Originally Posted by turboman123 

hello Tom
Nice info.
What about the case where we use the display to view pictures and movies that we take ourselves with a digital camera.. I do not know digital cameras that well. Do they have wider gamut capability, besides standard sRGB? If yes, would that make a case for wide gamut displays?

Originally Posted by TomHuffman 

4:2:2 and 4:4:4 are different types of chroma subsampling. In effect, color information is compressed during transmission and then uncompressed for display. In the overwhelming number of cases, your eyes should not be able to see the difference between them (Blu-ray is compressed even more at 4:2:0). Nonetheless, a lot of displays expect 4:2:2, so sending it in that format may reduce by one the number of format conversions required. The bottom line is that it shouldn't make any difference.

Originally Posted by TomHuffman 

There is a new standard that may be adopted for 4K material--Rec. 2020. You can see the specs here. Rec. 2020 requires at least 10-bit color.

For those who don't know, this just means that within the defined gamut there are a larger number of individual colors, each defined by a unique RGB triplet. 8-bit color, which is what we have been using for HD is 16-235 (I am ignoring above white and below black colors). This constitutes over 10,000,000 colors (219^3) and 219 shades of gray. 10-bit color is 64-940, which is 672 million colors (876^3) and 876 shades of gray. Note: this has nothing to do with the size of the gamut, but the number of discreet colors within the prescribed gamut.

Originally Posted by turboman123 

hello
I have a question about clipping. When setting contrast, clipping should be avoided. But I always wondered how to recognize clipping in Chromapure.

Here is how I do it. I measure greyscale and adjust offset and gain to get a good gresycale. Lets assume gain was adjusted to get a low dE deviation at and around 80IRE. If I see that R or G or B greyscale curve deviates downwards at 100%, then that would be an indication of clipping.
Question is what happens when R, G and B are clipping at the same time, and in the right proportion. Then I assume greyscale would stay perfect 100% but gamma goes up at 100%.
But I think this is only a theoretical case and in reality, R, G and B do not clip at the same time.
So greyscale is the one to watch.

That is how I would check for clipping. Is that OK? Any comments anyone?

Originally Posted by Geof 

I've used the Spears and Muncil disc to check for clipping...

Originally Posted by T3b_vat 

The AVS HD 709 disc is even easier and you can decide how much, if any, RGB clipping you allow. An excellent disc for this and many reasons.

Originally Posted by turboman123 

hello
Thanks for the reply. Unfortunately, I am a bit visually impaired, so I would like to rely on measurements.
Tom: can you please give me an input on how to use the capabilities of Chromapure for how to check for clipping. See my original post nr3886. Thanks.

Originally Posted by TomHuffman 

The only objective measurement for clipping is a dramatic drop-off in gamma at 90%.

Originally Posted by hungro 

How dramatic are we talking about?

Originally Posted by TomHuffman 

Windows 8

I just finished Windows 8 compliance testing using a Display 3 colorimeter and encountered no issues. CP runs fine using the new operating system.

Originally Posted by TomHuffman 

The only objective measurement for clipping is a dramatic drop-off in gamma at 90%.